A flat panel display possesses advantages of being ultra thin, power saved and radiation free and has been widely utilized. Present flat panel displays mainly comprise a LCD (Liquid Crystal Display) or an OLED (Organic Light Emitting Display).
To be compared with a well developed TFT-LCD, an OLED based on the Organic Light Emitting Diodes is an active light emitting display, which possesses outstanding properties of self-illumination, high contrast, wide view angle (up to 170°), fast response, high luminous efficiency, low operation voltage (3-10V), ultra-thin (thickness smaller than 2 mm) and etc. The display devices utilizing OLED technology has possibility to have a lighter, thinner, charming appearance, more excellent color display quality, wider view range and greater design flexibility.
Thin Film transistors (TFT) are important components of a flat panel display which can be formed on a glass substrate or a plastic substrate. Generally, the tin film transistors are employed as light switching-on elements and driving elements utilized such as LCDs, OLEDs, Electrophoresis Displays (EPD).
The oxide semiconductor TFT technology is the most popular skill at present. Because the carrier mobility of the oxide semiconductor is 20-30 times of the amorphous silicon semiconductor. With the higher electron mobility, it is capable of magnificently raising the charging/discharging rate of TFT to the pixel electrodes to promote the response speed of the pixels and to realize faster refreshing rate. In the mean time, the line scan rate of the pixels also can be promoted to make the manufacture of the flat panel display having ultra high resolution become possible. In comparison with the Low Temperature Poly-silicon (LTPS), the oxide semiconductor manufacture process is simpler and possesses higher compatibility with the amorphous silicon process. It can be applicable to the skill fields of Liquid Crystal Display, Organic Light Emitting Display, Flexible Display and etc. Because it fits the new generation production lines and has possible applications for displays with Large, Middle and Small sizes. The oxide semiconductor has the great opportunity of application development.
Generally, the present TFT substrate structure comprises a substrate, a gate, a gate isolation layer, an oxide semiconductor layer, an etching stopper layer, a source/a drain, a pixel electrode layer and etc. In the manufacture procedures, the formation of each layer structure requires one photolithography process and each photolithography process comprises processes of film formation, lithography, etching, stripping and etc. The lithography process further comprises processes of photoresistor coating, exposure and development and each lithography process requires creating one mask. The process becomes verbose, the manufacture skill is complicated and the production efficiency is lower; the more amount of masks is required, the higher the production cost became; meanwhile, the more the processes are involved, and the accumulated yield issue gets more significant.